@article{CMH_1944__17_138846,
     author = {Heinz Hopf},
     title = {\"Uber die {Bettischen} {Gruppen,} die zu einer beliebigen {Gruppe} geh\"oren.},
     journal = {Commentarii mathematici Helvetici},
     pages = {39--79},
     publisher = {mathdoc},
     volume = {17},
     year = {1944},
     zbl = {0061.40703},
     url = {http://geodesic.mathdoc.fr/item/CMH_1944__17_138846/}
}